Semiconductor memory devices, including flash memory, typically utilize memory cells to store data as an electrical value, such as an electrical charge or voltage. A flash memory cell, for example, includes a single transistor with a floating gate that is used to store a charge representative of a data value. Flash memory is a non-volatile data storage device that can be electrically erased and reprogrammed. More generally, non-volatile memory (e.g., flash memory, as well as other types of non-volatile memory implemented using any of a variety of technologies) retains stored information even when not powered, as opposed to volatile memory, which requires power to maintain the stored information.
While non-volatile memory retains data even when not powered, in some non-volatile memory systems, the data in each memory portion (e.g., a memory block) cannot be reliably read more than a predefined number of times, sometimes called a read disturb threshold, because the read operations “disturb” the stored data (e.g., change the amount of charge stored of floating gates of the transistors on which the data is stored). Thus, a problem arises when the number of read operations on a memory portion exceeds the read disturb threshold.